Directional synchronization in assisted millimeter wave systems

ABSTRACT

Certain aspects of the present disclosure provide techniques for assisted power control for an uplink signal transmitted during a RACH procedure. A UE may determine a transmit power for transmitting a message during a RACH procedure with a secondary BS, based at least in part, on communication between the UE and a primary BS. The UE may transmit the message to the second BS during the RACH procedure based, at least in part, on the determined transmit power.

CLAIM OF PRIORITY

The present Application for Patent is a continuation of U.S. patentapplication Ser. No. 15/789,633, filed Oct. 20, 2017 which claimsbenefit of U.S. Provisional Patent Application Ser. No. 62/411,416,filed Oct. 21, 2016 and U.S. Provisional Patent Application Ser. No.62/411,400, filed Oct. 21, 2016, assigned to the assignee hereof andhereby expressly incorporated by reference herein.

BACKGROUND Field of the Disclosure

Aspects of the present disclosure relate to wireless communications, andmore particularly, to a base station (BS) assisting a user equipment(UE) in establishing initial access and data transmissions with anotherBS.

Description of Related Art

Wireless communication systems are widely deployed to provide varioustelecommunication services such as telephony, video, data, messaging,and broadcasts. Typical wireless communication systems may employmultiple-access technologies capable of supporting communication withmultiple users by sharing available system resources (e.g., bandwidth,transmit power). Examples of such multiple-access technologies includeLong Term Evolution (LTE) systems, code division multiple access (CDMA)systems, time division multiple access (TDMA) systems, frequencydivision multiple access (FDMA) systems, orthogonal frequency divisionmultiple access (OFDMA) systems, single-carrier frequency divisionmultiple access (SC-FDMA) systems, and time division synchronous codedivision multiple access (TD-SCDMA) systems.

In some examples, a wireless multiple-access communication system mayinclude a number of base stations, each simultaneously supportingcommunication for multiple communication devices, otherwise known asuser equipment (UEs). In LTE or LTE-A network, a set of one or more basestations may define an eNodeB (eNB). In other examples (e.g., in a nextgeneration or 5G network), a wireless multiple access communicationsystem may include a number of distributed units (DUs) (e.g., edge units(EUs), edge nodes (ENs), radio heads (RHs), smart radio heads (SRHs),transmission reception points (TRPs), etc.) in communication with anumber of central units (CUs) (e.g., central nodes (CNs), access nodecontrollers (ANCs), etc.), where a set of one or more distributed units,in communication with a central unit, may define an access node (e.g., anew radio base station (NR BS), a new radio node-B (NR NB), a networknode, 5G NB, gNB, etc.). A base station or DU may communicate with a setof UEs on downlink channels (e.g., for transmissions from a base stationor to a UE) and uplink channels (e.g., for transmissions from a UE to abase station or distributed unit).

These multiple access technologies have been adopted in varioustelecommunication standards to provide a common protocol that enablesdifferent wireless devices to communicate on a municipal, national,regional, and even global level. An example of an emergingtelecommunication standard is new radio (NR), for example, 5G radioaccess. NR is a set of enhancements to the LTE mobile standardpromulgated by Third Generation Partnership Project (3GPP). NR isdesigned to better support mobile broadband Internet access by improvingspectral efficiency, lowering costs, improving services, making use ofnew spectrum, and better integrating with other open standards usingOFDMA with a cyclic prefix (CP) on the downlink (DL) and on the uplink(UL) as well as support beamforming, multiple-input multiple-output(MIMO) antenna technology, and carrier aggregation.

However, as the demand for mobile broadband access continues toincrease, there exists a need for further improvements in NR technology.These improvements may be applicable to other multi-access technologiesand the telecommunication standards that employ these technologies.

SUMMARY

The systems, methods, and devices of the disclosure each have severalaspects, no single one of which is solely responsible for its desirableattributes. Without limiting the scope of this disclosure as expressedby the claims which follow, some features will now be discussed briefly.After considering this discussion, and particularly after reading thesection entitled “Detailed Description” one will understand how thefeatures of this disclosure provide advantages that include improvedcommunications between access points and stations in a wireless network.

Certain aspects of the present disclosure relate to methods andapparatus for assisting a UE in performing initial access to a BS. Asdescribed herein, a first BS may communicate with at least one userequipments (UEs) in a first frequency spectrum, allocate resources tothe at least one UE for participating in at least one of assisteddirectional initial access, beam management, mobility management, radioresource management (RRM), or radio link monitoring (RLM) in a secondfrequency spectrum, and provide configuration information to the atleast one UE for at least one of a directional synchronization signal, abeam reference signal (e.g. CSI-RS), or a random access message (e.g.RACH preamble, message2, message3, or message4) to be transmitted aspart of the assisted directional initial access, beam management,mobility management, RRM or RLM.

Certain aspects of the present disclosure relate to methods andapparatus for assisting a UE in performing at least one of initialaccess, beam management, RRM, or RLM by a UE. As described herein, theUE may communicate with a first base station (BS) in a first frequencyspectrum, receive an allocation of resources and configurationinformation from the first BS for a at least one of a directionalsynchronization signal, a beam reference signal, or a random accessmessage to be used by a second BS operating in a second frequencyspectrum as part of at least one of an initial access, beam management,mobility management, RRM, or RLM procedures, wherein the configurationinformation is specific to the UE or to a set of UEs including the UE,and participate in the at least one of initial access, beam management,mobility management, RRM, or RLM procedures with the second BS inaccordance with the configuration information.

Certain aspects of the present disclosure relate to methods andapparatus for a BS to participate in at least one of initial access,beam management, RRM, or RLM procedures with a UE. As described herein,the BS may determine an allocation of resources and configurationinformation for at least one of a directional synchronization signal, abeam reference signal, a random access message to be used by a userequipment (UE) and the BS in a first frequency spectrum as part of atleast one of an initial access, beam management, mobility management,RRM, or RLM procedures, wherein the configuration information isspecific to the UE or to a set of UEs including the UE participate inthe at least one of initial access, beam management, mobilitymanagement, RRM, or RLM procedures with the UE in accordance with theconfiguration information.

Aspects generally include methods, apparatus, systems, computer readablemediums, and processing systems, as substantially described herein withreference to and as illustrated by the accompanying drawings.

To the accomplishment of the foregoing and related ends, the one or moreaspects comprise the features hereinafter fully described andparticularly pointed out in the claims. The following description andthe annexed drawings set forth in detail certain illustrative featuresof the one or more aspects. These features are indicative, however, ofbut a few of the various ways in which the principles of various aspectsmay be employed, and this description is intended to include all suchaspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentdisclosure can be understood in detail, a more particular description,briefly summarized above, may be had by reference to aspects, some ofwhich are illustrated in the appended drawings. It is to be noted,however, that the appended drawings illustrate only certain typicalaspects of this disclosure and are therefore not to be consideredlimiting of its scope, for the description may admit to other equallyeffective aspects.

FIG. 1 is a block diagram conceptually illustrating an exampletelecommunications system, in accordance with certain aspects of thepresent disclosure.

FIG. 2 is a block diagram illustrating an example logical architectureof a distributed RAN, in accordance with certain aspects of the presentdisclosure.

FIG. 3 is a diagram illustrating an example physical architecture of adistributed RAN, in accordance with certain aspects of the presentdisclosure.

FIG. 4 is a block diagram conceptually illustrating a design of anexample BS and user equipment (UE), in accordance with certain aspectsof the present disclosure.

FIG. 5 is a diagram showing examples for implementing a communicationprotocol stack, in accordance with certain aspects of the presentdisclosure.

FIG. 6 illustrates an example of a DL-centric subframe, in accordancewith certain aspects of the present disclosure.

FIG. 7 illustrates an example of an UL-centric subframe, in accordancewith certain aspects of the present disclosure.

FIG. 8 illustrates an example wireless communication system, in whichaspects of the present disclosure may be implemented.

FIG. 9 illustrates an example of assisted initial access in a millimeterwave system, in accordance with certain aspects of the presentdisclosure.

FIG. 10 illustrates another example of assisted initial access in amillimeter wave system, in accordance with certain aspects of thepresent disclosure.

FIG. 11 illustrates example operations performed by a base station toassist a UE in initial access with another base station, in accordancewith certain aspects of the present disclosure.

FIG. 12 illustrates example operations performed by a UE, in accordancewith certain aspects of the present disclosure.

FIG. 13 illustrates example operations performed by a base station forinitial access with a UE, in accordance with certain aspects of thepresent disclosure.

FIGS. 14-16 illustrate example operations for utilizing multiple sets ofresources and configurations, in accordance with certain aspects of thepresent disclosure.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements described in one aspectmay be beneficially utilized on other aspects without specificrecitation.

DETAILED DESCRIPTION

Aspects of the present disclosure provide apparatus, methods, processingsystems, and computer readable mediums for new radio (NR) (new radioaccess technology or 5G technologies).

NR may support various wireless communication services, such as Enhancedmobile broadband (eMBB) targeting wide bandwidth (e.g. 80 MHz beyond),millimeter wave (mmW) targeting high carrier frequency (e.g. 27 GHz orbeyond), massive MTC (mMTC) targeting non-backward compatible MTCtechniques, and/or mission critical targeting ultra-reliable low latencycommunications (URLLC). These services may include latency andreliability requirements. These services may also have differenttransmission time intervals (TTI) to meet respective quality of service(QoS) requirements. In addition, these services may co-exist in the samesubframe.

The following description provides examples, and is not limiting of thescope, applicability, or examples set forth in the claims. Changes maybe made in the function and arrangement of elements discussed withoutdeparting from the scope of the disclosure. Various examples may omit,substitute, or add various procedures or components as appropriate. Forinstance, the methods described may be performed in an order differentfrom that described, and various steps may be added, omitted, orcombined. Also, features described with respect to some examples may becombined in some other examples. For example, an apparatus may beimplemented or a method may be practiced using any number of the aspectsset forth herein. In addition, the scope of the disclosure is intendedto cover such an apparatus or method which is practiced using otherstructure, functionality, or structure and functionality in addition toor other than the various aspects of the disclosure set forth herein. Itshould be understood that any aspect of the disclosure described hereinmay be embodied by one or more elements of a claim. The word “exemplary”is used herein to mean “serving as an example, instance, orillustration.” Any aspect described herein as “exemplary” is notnecessarily to be construed as preferred or advantageous over otheraspects.

The techniques described herein may be used for various wirelesscommunication networks such as LTE, CDMA, TDMA, FDMA, OFDMA, SC-FDMA andother networks. The terms “network” and “system” are often usedinterchangeably. A CDMA network may implement a radio technology such asUniversal Terrestrial Radio Access (UTRA), cdma2000, etc. UTRA includesWideband CDMA (WCDMA) and other variants of CDMA. Cdma2000 coversIS-2000, IS-95 and IS-856 standards. A TDMA network may implement aradio technology such as Global System for Mobile Communications (GSM).An OFDMA network may implement a radio technology such as NR (e.g. 5GRA), Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11(Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDMA, etc. UTRA andE-UTRA are part of Universal Mobile Telecommunication System (UMTS). NRis an emerging wireless communications technology under development inconjunction with the 5G Technology Forum (5GTF). 3GPP Long TermEvolution (LTE) and LTE-Advanced (LTE-A) are releases of UMTS that useE-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM are described indocuments from an organization named “3rd Generation PartnershipProject” (3GPP). Cdma2000 and UMB are described in documents from anorganization named “3rd Generation Partnership Project 2” (3GPP2). Thetechniques described herein may be used for the wireless networks andradio technologies mentioned above as well as other wireless networksand radio technologies. For clarity, while aspects may be describedherein using terminology commonly associated with 3G and/or 4G wirelesstechnologies, aspects of the present disclosure can be applied in othergeneration-based communication systems, such as 5G and later, includingNR technologies.

Example Wireless Communications System

FIG. 1 illustrates an example wireless network 100 in which aspects ofthe present disclosure may be performed. For example, the wirelessnetwork may be a new radio (NR) or 5G networks. NR wirelesscommunication systems may employ beams, where a BS and UE communicatevia active beams. In scenarios where a BS may communicate with a UEusing active beams, the UE may benefit from assistance in determining atransmit power to use for transmitting a message during a random accesschannel (RACH) procedure.

Aspects of the present disclosure provide techniques and apparatus forassisting a UE in determining a transmit power for use during a RACHprocedure. According to one example, a UE may want to establishcommunication with a BS operating in a millimeter-wave (mmWave)frequency spectrum. The UE may receive assistance information fordetermining the transmit power to use during the RACH procedure from aBS operating in a lower frequency spectrum than the mmWave spectrum.

For illustrative purposes, aspects are described with reference to aprimary BS and a secondary BS, wherein the secondary BS operates in anmmWave frequency spectrum and the primary BS operations in a lowerfrequency spectrum that the secondary spectrum; however, aspects may notbe limited to this example scenario.

More generically, the UE may receive assistance information from one BSthat may be used to determine power control for transmissions during aRACH procedure with another BS. The BS providing the assistanceinformation may operate in a different frequency spectrum than the BS towhich the UE transmits the RACH signaling using the determined powercontrol.

As described herein, for example, with respect to FIG. 8, proceduresrelated a UE communicating with a BS via multiple beams, such as initialaccess and data transmissions, including (but not limited to) beammanagement, mobility management, RRM, and/or RLM may be simplified withassistance from a BS operating in a lower frequency spectrum. With theassistance of the BS operating in a lower frequency spectrum, mmWaveresources may be conserved and, in certain scenarios, initialsynchronization to the mmWave network may be completely or partlybypassed.

UEs 120 may be configured to perform the operations 900 and methodsdescribed herein for determining a transmit power. BS 110 may comprise atransmission reception point (TRP), Node B (NB), 5G NB, access point(AP), new radio (NR) BS, Master BS, primary BS, etc.). The NR network100 may include the central unit. The BS 110 may perform the operations1000 and other methods described herein for providing assistance to a UEin determining a transmit power to use during a RACH procedure withanother BS (e.g., a secondary BS).

A UE 120 may determine a transmit power for transmitting a messageduring a RACH procedure with a secondary BS, based at least in part, oncommunication between the UE and a primary BS. The UE may transmit themessage to the secondary BS during the RACH procedure based, at least inpart, on the determined transmit power.

A BS 110, such as a master BS or a primary BS, may communicate with theUE and may take one or more actions to assist the UE in setting atransmit power for transmitting a message during the RACH procedure witha secondary BS.

As illustrated in FIG. 1, the wireless network 100 may include a numberof BSs 110 and other network entities. According to one example, thenetwork entities including the BS and UEs may communicate on highfrequencies (e.g., >6 GHz) using beams. One or more BS may alsocommunicate at a lower frequency (e.g., <6 GHz). The one or more BSconfigured to operate in a high frequency spectrum and the one or moreBS configured to operate in a lower frequency spectrum may beco-located.

A BS may be a station that communicates with UEs. Each BS 110 mayprovide communication coverage for a particular geographic area. In3GPP, the term “cell” can refer to a coverage area of a Node B and/or aNode B subsystem serving this coverage area, depending on the context inwhich the term is used. In NR systems, the term “cell” and gNB, Node B,5G NB, AP, NR BS, NR BS, or TRP may be interchangeable. In someexamples, a cell may not necessarily be stationary, and the geographicarea of the cell may move according to the location of a mobile basestation. In some examples, the base stations may be interconnected toone another and/or to one or more other base stations or network nodes(not shown) in the wireless network 100 through various types ofbackhaul interfaces such as a direct physical connection, a virtualnetwork, or the like using any suitable transport network.

In general, any number of wireless networks may be deployed in a givengeographic area. Each wireless network may support a particular radioaccess technology (RAT) and may operate on one or more frequencies. ARAT may also be referred to as a radio technology, an air interface,etc. A frequency may also be referred to as a carrier, a frequencychannel, etc. Each frequency may support a single RAT in a givengeographic area in order to avoid interference between wireless networksof different RATs. In some cases, NR or 5G RAT networks may be deployed.

A BS may provide communication coverage for a macro cell, a pico cell, afemto cell, and/or other types of cell. A macro cell may cover arelatively large geographic area (e.g., several kilometers in radius)and may allow unrestricted access by UEs with service subscription. Apico cell may cover a relatively small geographic area and may allowunrestricted access by UEs with service subscription. A femto cell maycover a relatively small geographic area (e.g., a home) and may allowrestricted access by UEs having association with the femto cell (e.g.,UEs in a Closed Subscriber Group (CSG), UEs for users in the home,etc.). A BS for a macro cell may be referred to as a macro BS. A BS fora pico cell may be referred to as a pico BS. A BS for a femto cell maybe referred to as a femto BS or a home BS. In the example shown in FIG.1, the BSs 110 a, 110 b and 110 c may be macro BSs for the macro cells102 a, 102 b and 102 c, respectively. The BS 110 x may be a pico BS fora pico cell 102 x. The BSs 110 y and 110 z may be femto BS for the femtocells 102 y and 102 z, respectively. A BS may support one or multiple(e.g., three) cells.

The wireless network 100 may also include relay stations. A relaystation is a station that receives a transmission of data and/or otherinformation from an upstream station (e.g., a BS or a UE) and sends atransmission of the data and/or other information to a downstreamstation (e.g., a UE or a BS). A relay station may also be a UE thatrelays transmissions for other UEs. In the example shown in FIG. 1, arelay station 110 r may communicate with the BS 110 a and a UE 120 r inorder to facilitate communication between the BS 110 a and the UE 120 r.A relay station may also be referred to as a relay BS, a relay, etc.

The wireless network 100 may be a heterogeneous network that includesBSs of different types, e.g., macro BS, pico BS, femto BS, relays, etc.These different types of BSs may have different transmit power levels,different coverage areas, and different impact on interference in thewireless network 100. For example, macro BS may have a high transmitpower level (e.g., 20 Watts) whereas pico BS, femto BS, and relays mayhave a lower transmit power level (e.g., 1 Watt).

The wireless network 100 may support synchronous or asynchronousoperation. For synchronous operation, the BSs may have similar frametiming, and transmissions from different BSs may be approximatelyaligned in time. For asynchronous operation, the BSs may have differentframe timing, and transmissions from different BSs may not be aligned intime. The techniques described herein may be used for both synchronousand asynchronous operation.

A network controller 130 may couple to a set of BSs and providecoordination and control for these BSs. The network controller 130 maycommunicate with the BSs 110 via a backhaul. The BSs 110 may alsocommunicate with one another, e.g., directly or indirectly via wirelessor wireline backhaul.

The UEs 120 (e.g., 120 x, 120 y, etc.) may be dispersed throughout thewireless network 100, and each UE may be stationary or mobile. A UE mayalso be referred to as a mobile station, a terminal, an access terminal,a subscriber unit, a station, a Customer Premises Equipment (CPE), acellular phone, a smart phone, a personal digital assistant (PDA), awireless modem, a wireless communication device, a handheld device, alaptop computer, a cordless phone, a wireless local loop (WLL) station,a tablet, a camera, a gaming device, a netbook, a smartbook, anultrabook, a medical device or medical equipment, a biometricsensor/device, a wearable device such as a smart watch, smart clothing,smart glasses, a smart wrist band, smart jewelry (e.g., a smart ring, asmart bracelet, etc.), an entertainment device (e.g., a music device, avideo device, a satellite radio, etc.), a vehicular component or sensor,a smart meter/sensor, industrial manufacturing equipment, a globalpositioning system device, or any other suitable device that isconfigured to communicate via a wireless or wired medium. Some UEs maybe considered evolved or machine-type communication (MTC) devices orevolved MTC (eMTC) devices. MTC and eMTC UEs include, for example,robots, drones, remote devices, sensors, meters, monitors, locationtags, etc., that may communicate with a BS, another device (e.g., remotedevice), or some other entity. A wireless node may provide, for example,connectivity for or to a network (e.g., a wide area network such asInternet or a cellular network) via a wired or wireless communicationlink. Some UEs may be considered Internet-of-Things (IoT) devices.

In FIG. 1, a solid line with double arrows indicates desiredtransmissions between a UE and a serving BS, which is a BS designated toserve the UE on the downlink and/or uplink. A dashed line with doublearrows indicates interfering transmissions between a UE and a BS.

Certain wireless networks (e.g., LTE) utilize orthogonal frequencydivision multiplexing (OFDM) on the downlink and single-carrierfrequency division multiplexing (SC-FDM) on the uplink. OFDM and SC-FDMpartition the system bandwidth into multiple (K) orthogonal subcarriers,which are also commonly referred to as tones, bins, etc. Each subcarriermay be modulated with data. In general, modulation symbols are sent inthe frequency domain with OFDM and in the time domain with SC-FDM. Thespacing between adjacent subcarriers may be fixed, and the total numberof subcarriers (K) may be dependent on the system bandwidth. Forexample, the spacing of the subcarriers may be 15 kHz and the minimumresource allocation (called a ‘resource block’) may be 12 subcarriers(or 180 kHz). Consequently, the nominal FFT size may be equal to 128,256, 512, 1024 or 2048 for system bandwidth of 1.25, 2.5, 5, 10 or 20megahertz (MHz), respectively. The system bandwidth may also bepartitioned into subbands. For example, a subband may cover 1.08 MHz(i.e., 6 resource blocks), and there may be 1, 2, 4, 8 or 16 subbandsfor system bandwidth of 1.25, 2.5, 5, 10 or 20 MHz, respectively.

While aspects of the examples described herein may be associated withLTE technologies, aspects of the present disclosure may be applicablewith other wireless communications systems, such as NR.

NR may utilize OFDM with a CP on the uplink and downlink and includesupport for half-duplex operation using TDD. A single component carrierbandwidth of 100 MHz may be supported. NR resource blocks may span 12sub-carriers with a subcarrier bandwidth of 75 kHz over a 0.1 msduration. Each radio frame may consist of 2 half frames, each half frameconsisting of 5 subframes, with a length of 10 ms. Consequently, eachsubframe may have a length of 0.2 ms. Each subframe may indicate a linkdirection (i.e., DL or UL) for data transmission and the link directionfor each subframe may be dynamically switched. Each subframe may includeDL/UL data as well as DL/UL control data. UL and DL subframes for NR maybe as described in more detail below with respect to FIGS. 6 and 7.Beamforming may be supported and beam direction may be dynamicallyconfigured. MIMO transmissions with precoding may also be supported.MIMO configurations in the DL may support up to 8 transmit antennas withmulti-layer DL transmissions up to 8 streams and up to 2 streams per UE.Multi-layer transmissions with up to 2 streams per UE may be supported.Aggregation of multiple cells may be supported with up to 8 servingcells. Alternatively, NR may support a different air interface, otherthan an OFDM-based. NR networks may include entities such CUs and/orDUs.

In some examples, access to the air interface may be scheduled, whereina scheduling entity (e.g., a base station) allocates resources forcommunication among some or all devices and equipment within its servicearea or cell. Within the present disclosure, as discussed further below,the scheduling entity may be responsible for scheduling, assigning,reconfiguring, and releasing resources for one or more subordinateentities. That is, for scheduled communication, subordinate entitiesutilize resources allocated by the scheduling entity. Base stations arenot the only entities that may function as a scheduling entity. That is,in some examples, a UE may function as a scheduling entity, schedulingresources for one or more subordinate entities (e.g., one or more otherUEs). In this example, the UE is functioning as a scheduling entity, andother UEs utilize resources scheduled by the UE for wirelesscommunication. A UE may function as a scheduling entity in apeer-to-peer (P2P) network, and/or in a mesh network. In a mesh networkexample, UEs may optionally communicate directly with one another inaddition to communicating with the scheduling entity.

Thus, in a wireless communication network with a scheduled access totime-frequency resources and having a cellular configuration, a P2Pconfiguration, and a mesh configuration, a scheduling entity and one ormore subordinate entities may communicate utilizing the scheduledresources.

As noted above, a RAN may include a CU and DUs. A NR BS (e.g., gNB, 5GNode B, Node B, transmission reception point (TRP), access point (AP))may correspond to one or multiple BSs. NR cells can be configured asaccess cell (ACells) or data only cells (DCells). For example, the RAN(e.g., a central unit or distributed unit) can configure the cells.DCells may be cells used for carrier aggregation or dual connectivity,but not used for initial access, cell selection/reselection, orhandover. In some cases DCells may not transmit synchronizationsignals—in some case cases DCells may transmit SS. NR BSs may transmitdownlink signals to UEs indicating the cell type. Based on the cell typeindication, the UE may communicate with the NR BS. For example, the UEmay determine NR BSs to consider for cell selection, access, handover,and/or measurement based on the indicated cell type.

FIG. 2 illustrates an example logical architecture of a distributedradio access network (RAN) 200, which may be implemented in the wirelesscommunication system illustrated in FIG. 1. A 5G access node 206 mayinclude an access node controller (ANC) 202. The ANC may be a centralunit (CU) of the distributed RAN 200. The backhaul interface to the nextgeneration core network (NG-CN) 204 may terminate at the ANC. Thebackhaul interface to neighboring next generation access nodes (NG-ANs)may terminate at the ANC. The ANC may include one or more TRPs 208(which may also be referred to as BSs, NR BSs, Node Bs, 5G NBs, APs, orsome other term). As described above, a TRP may be used interchangeablywith “cell.”

The TRPs 208 may be a DU. The TRPs may be connected to one ANC (ANC 202)or more than one ANC (not illustrated). For example, for RAN sharing,radio as a service (RaaS), and service specific AND deployments, the TRPmay be connected to more than one ANC. A TRP may include one or moreantenna ports. The TRPs may be configured to individually (e.g., dynamicselection) or jointly (e.g., joint transmission) serve traffic to a UE.

The local architecture 200 may be used to illustrate fronthauldefinition. The architecture may be defined that support fronthaulingsolutions across different deployment types. For example, thearchitecture may be based on transmit network capabilities (e.g.,bandwidth, latency, and/or jitter).

The architecture may share features and/or components with LTE.According to aspects, the next generation AN (NG-AN) 210 may supportdual connectivity with NR. The NG-AN may share a common fronthaul forLTE and NR.

The architecture may enable cooperation between and among TRPs 208. Forexample, cooperation may be preset within a TRP and/or across TRPs viathe ANC 202. According to aspects, no inter-TRP interface may beneeded/present.

According to aspects, a dynamic configuration of split logical functionsmay be present within the architecture 200. As will be described in moredetail with reference to FIG. 5, the Radio Resource Control (RRC) layer,Packet Data Convergence Protocol (PDCP) layer, Radio Link Control (RLC)layer, Medium Access Control (MAC) layer, and a Physical (PHY) layersmay be adaptably placed at the DU or CU (e.g., TRP or ANC,respectively). According to certain aspects, a BS may include a centralunit (CU) (e.g., ANC 202) and/or one or more distributed units (e.g.,one or more TRPs 208).

FIG. 3 illustrates an example physical architecture of a distributed RAN300, according to aspects of the present disclosure. A centralized corenetwork unit (C-CU) 302 may host core network functions. The C-CU may becentrally deployed. C-CU functionality may be offloaded (e.g., toadvanced wireless services (AWS)), in an effort to handle peak capacity.

A centralized RAN unit (C-RU) 304 may host one or more ANC functions.Optionally, the C-RU may host core network functions locally. The C-RUmay have distributed deployment. The C-RU may be closer to the networkedge.

A DU 306 may host one or more TRPs (edge node (EN), an edge unit (EU), aradio head (RH), a smart radio head (SRH), or the like). The DU may belocated at edges of the network with radio frequency (RF) functionality.

FIG. 4 illustrates example components of the BS 110 and UE 120illustrated in FIG. 1, which may be used to implement aspects of thepresent disclosure. The BS may include a TRP and may be referred to as aMaster eNB (MeNB) (e.g., Master BS, primary BS). According to aspects,the Master BS may operate at lower frequencies, for example, below 6 GHzand a Secondary BS may operate at higher frequencies, for example,mmWave frequencies above 6 GHz. The Master BS and the Secondary BS maybe geographically co-located.

One or more components of the BS 110 and UE 120 may be used to practiceaspects of the present disclosure. For example, antennas 452, Tx/Rx 454,processors 466, 458, 464, and/or controller/processor 480 of the UE 120and/or antennas 434, processors 420, 430, 438, and/orcontroller/processor 440 of the BS 110 may be used to perform theoperations described herein and illustrated with reference to FIGS.9-10.

FIG. 4 shows a block diagram of a design of a BS 110 and a UE 120, whichmay be one of the BSs and one of the UEs in FIG. 1. For a restrictedassociation scenario, the base station 110 may be the macro BS 110 c inFIG. 1, and the UE 120 may be the UE 120 y. The base station 110 mayalso be a base station of some other type. The base station 110 may beequipped with antennas 434 a through 434 t, and the UE 120 may beequipped with antennas 452 a through 452 r.

At the base station 110, a transmit processor 420 may receive data froma data source 412 and control information from a controller/processor440. The control information may be for the Physical Broadcast Channel(PBCH), Physical Control Format Indicator Channel (PCFICH), PhysicalHybrid ARQ Indicator Channel (PHICH), Physical Downlink Control Channel(PDCCH), etc. The data may be for the Physical Downlink Shared Channel(PDSCH), etc. The processor 420 may process (e.g., encode and symbolmap) the data and control information to obtain data symbols and controlsymbols, respectively. The processor 420 may also generate referencesymbols, e.g., for the PSS, SSS, and cell-specific reference signal(CRS). A transmit (TX) multiple-input multiple-output (MIMO) processor430 may perform spatial processing (e.g., precoding) on the datasymbols, the control symbols, and/or the reference symbols, ifapplicable, and may provide output symbol streams to the modulators(MODs) 432 a through 432 t. Each modulator 432 may process a respectiveoutput symbol stream (e.g., for OFDM, etc.) to obtain an output samplestream. Each modulator 432 may further process (e.g., convert to analog,amplify, filter, and upconvert) the output sample stream to obtain adownlink signal. Downlink signals from modulators 432 a through 432 tmay be transmitted via the antennas 434 a through 434 t, respectively.

At the UE 120, the antennas 452 a through 452 r may receive the downlinksignals from the base station 110 and may provide received signals tothe demodulators (DEMODs) 454 a through 454 r, respectively. Eachdemodulator 454 may condition (e.g., filter, amplify, downconvert, anddigitize) a respective received signal to obtain input samples. Eachdemodulator 454 may further process the input samples (e.g., for OFDM,etc.) to obtain received symbols. A MIMO detector 456 may obtainreceived symbols from all the demodulators 454 a through 454 r, performMIMO detection on the received symbols if applicable, and providedetected symbols. A receive processor 458 may process (e.g., demodulate,deinterleave, and decode) the detected symbols, provide decoded data forthe UE 120 to a data sink 460, and provide decoded control informationto a controller/processor 480.

On the uplink, at the UE 120, a transmit processor 464 may receive andprocess data (e.g., for the Physical Uplink Shared Channel (PUSCH)) froma data source 462 and control information (e.g., for the Physical UplinkControl Channel (PUCCH) from the controller/processor 480. The transmitprocessor 464 may also generate reference symbols for a referencesignal. The symbols from the transmit processor 464 may be precoded by aTX MIMO processor 466 if applicable, further processed by thedemodulators 454 a through 454 r (e.g., for SC-FDM, etc.), andtransmitted to the base station 110. At the BS 110, the uplink signalsfrom the UE 120 may be received by the antennas 434, processed by themodulators 432, detected by a MIMO detector 436 if applicable, andfurther processed by a receive processor 438 to obtain decoded data andcontrol information sent by the UE 120. The receive processor 438 mayprovide the decoded data to a data sink 439 and the decoded controlinformation to the controller/processor 440.

The controllers/processors 440 and 480 may direct the operation at thebase station 110 and the UE 120, respectively. The processor 440 and/orother processors and modules at the base station 110 may perform ordirect, e.g., the execution of the functional blocks illustrated in FIG.9, and/or other processes for the techniques described herein. Thememories 442 and 482 may store data and program codes for the BS 110 andthe UE 120, respectively. A scheduler 444 may schedule UEs for datatransmission on the downlink and/or uplink.

FIG. 5 illustrates a diagram 500 showing examples for implementing acommunications protocol stack, according to aspects of the presentdisclosure. The illustrated communications protocol stacks may beimplemented by devices operating in a in a 5G system. Diagram 500illustrates a communications protocol stack including a Radio ResourceControl (RRC) layer 510, a Packet Data Convergence Protocol (PDCP) layer515, a Radio Link Control (RLC) layer 520, a Medium Access Control (MAC)layer 525, and a Physical (PHY) layer 530. In various examples thelayers of a protocol stack may be implemented as separate modules ofsoftware, portions of a processor or ASIC, portions of non-collocateddevices connected by a communications link, or various combinationsthereof. Collocated and non-collocated implementations may be used, forexample, in a protocol stack for a network access device (e.g., ANs,CUs, and/or DUs) or a UE.

A first option 505-a shows a split implementation of a protocol stack,in which implementation of the protocol stack is split between acentralized network access device (e.g., an ANC 202 in FIG. 2) anddistributed network access device (e.g., DU 208 in FIG. 2). In the firstoption 505-a, an RRC layer 510 and a PDCP layer 515 may be implementedby the central unit, and an RLC layer 520, a MAC layer 525, and a PHYlayer 530 may be implemented by the DU. In various examples the CU andthe DU may be collocated or non-collocated. The first option 505-a maybe useful in a macro cell, micro cell, or pico cell deployment.

A second option 505-b shows a unified implementation of a protocolstack, in which the protocol stack is implemented in a single networkaccess device (e.g., access node (AN), new radio base station (NR BS), anew radio Node-B (NR NB), a network node (NN), or the like.). In thesecond option, the RRC layer 510, the PDCP layer 515, the RLC layer 520,the MAC layer 525, and the PHY layer 530 may each be implemented by theAN. The second option 505-b may be useful in a femto cell deployment.

Regardless of whether a network access device implements part or all ofa protocol stack, a UE may implement an entire protocol stack (e.g., theRRC layer 510, the PDCP layer 515, the RLC layer 520, the MAC layer 525,and the PHY layer 530).

FIG. 6 is a diagram 600 showing an example of a DL-centric subframe. TheDL-centric subframe may include a control portion 602. The controlportion 602 may exist in the initial or beginning portion of theDL-centric subframe. The control portion 602 may include variousscheduling information and/or control information corresponding tovarious portions of the DL-centric subframe. In some configurations, thecontrol portion 602 may be a physical DL control channel (PDCCH), asindicated in FIG. 6. The DL-centric subframe may also include a DL dataportion 604. The DL data portion 604 may sometimes be referred to as thepayload of the DL-centric subframe. The DL data portion 604 may includethe communication resources utilized to communicate DL data from thescheduling entity (e.g., UE or BS) to the subordinate entity (e.g., UE).In some configurations, the DL data portion 604 may be a physical DLshared channel (PDSCH).

The DL-centric subframe may also include a common UL portion 606. Thecommon UL portion 606 may sometimes be referred to as an UL burst, acommon UL burst, and/or various other suitable terms. The common ULportion 606 may include feedback information corresponding to variousother portions of the DL-centric subframe. For example, the common ULportion 606 may include feedback information corresponding to thecontrol portion 602. Non-limiting examples of feedback information mayinclude an ACK signal, a NACK signal, a HARQ indicator, and/or variousother suitable types of information. The common UL portion 606 mayinclude additional or alternative information, such as informationpertaining to random access channel (RACH) procedures, schedulingrequests (SRs), and various other suitable types of information. Asillustrated in FIG. 6, the end of the DL data portion 604 may beseparated in time from the beginning of the common UL portion 606. Thistime separation may sometimes be referred to as a gap, a guard period, aguard interval, and/or various other suitable terms. This separationprovides time for the switch-over from DL communication (e.g., receptionoperation by the subordinate entity (e.g., UE)) to UL communication(e.g., transmission by the subordinate entity (e.g., UE)). One ofordinary skill in the art will understand that the foregoing is merelyone example of a DL-centric subframe and alternative structures havingsimilar features may exist without necessarily deviating from theaspects described herein.

FIG. 7 is a diagram 700 showing an example of an UL-centric subframe.The UL-centric subframe may include a control portion 702. The controlportion 702 may exist in the initial or beginning portion of theUL-centric subframe. The control portion 702 in FIG. 7 may be similar tothe control portion described above with reference to FIG. 6. TheUL-centric subframe may also include an UL data portion 704. The UL dataportion 704 may sometimes be referred to as the payload of theUL-centric subframe. The UL portion may refer to the communicationresources utilized to communicate UL data from the subordinate entity(e.g., UE) to the scheduling entity (e.g., UE or BS). In someconfigurations, the control portion 702 may be a physical DL controlchannel (PDCCH).

As illustrated in FIG. 7, the end of the control portion 702 may beseparated in time from the beginning of the UL data portion 704. Thistime separation may sometimes be referred to as a gap, guard period,guard interval, and/or various other suitable terms. This separationprovides time for the switch-over from DL communication (e.g., receptionoperation by the scheduling entity) to UL communication (e.g.,transmission by the scheduling entity). The UL-centric subframe may alsoinclude a common UL portion 706. The common UL portion 706 in FIG. 7 maybe similar to the common UL portion 706 described above with referenceto FIG. 7. The common UL portion 706 may additional or alternativeinclude information pertaining to channel quality indicator (CQI),sounding reference signals (SRSs), and various other suitable types ofinformation. One of ordinary skill in the art will understand that theforegoing is merely one example of an UL-centric subframe andalternative structures having similar features may exist withoutnecessarily deviating from the aspects described herein.

In some circumstances, two or more subordinate entities (e.g., UEs) maycommunicate with each other using sidelink signals. Real-worldapplications of such sidelink communications may include public safety,proximity services, UE-to-network relaying, vehicle-to-vehicle (V2V)communications, Internet of Everything (IoE) communications, IoTcommunications, mission-critical mesh, and/or various other suitableapplications. Generally, a sidelink signal may refer to a signalcommunicated from one subordinate entity (e.g., UE1) to anothersubordinate entity (e.g., UE2) without relaying that communicationthrough the scheduling entity (e.g., UE or BS), even though thescheduling entity may be utilized for scheduling and/or controlpurposes. In some examples, the sidelink signals may be communicatedusing a licensed spectrum (unlike wireless local area networks, whichtypically use an unlicensed spectrum).

A UE may operate in various radio resource configurations, including aconfiguration associated with transmitting pilots using a dedicated setof resources (e.g., a radio resource control (RRC) dedicated state,etc.) or a configuration associated with transmitting pilots using acommon set of resources (e.g., an RRC common state, etc.). Whenoperating in the RRC dedicated state, the UE may select a dedicated setof resources for transmitting a pilot signal to a network. Whenoperating in the RRC common state, the UE may select a common set ofresources for transmitting a pilot signal to the network. In eithercase, a pilot signal transmitted by the UE may be received by one ormore network access devices, such as an AN, or a DU, or portionsthereof. Each receiving network access device may be configured toreceive and measure pilot signals transmitted on the common set ofresources, and also receive and measure pilot signals transmitted ondedicated sets of resources allocated to the UEs for which the networkaccess device is a member of a monitoring set of network access devicesfor the UE. One or more of the receiving network access devices, or a CUto which receiving network access device(s) transmit the measurements ofthe pilot signals, may use the measurements to identify serving cellsfor the UEs, or to initiate a change of serving cell for one or more ofthe UEs.

Example Assisted mmWave Access

FIG. 8 illustrates an example 800 of an assisted mmWave access process(or a beam management, mobility management, radio resource management(RRM), or radio link monitoring (RLM) procedure). A UE 802 may want toaccess a BS 806. The BS 806 may be a secondary BS that for exampleoperates in an mmWave spectrum. Another BS, such as BS 804, may assistthe UE in accessing the BS 806. According to an example, BS 804 may be aprimary BS that operates in a lower frequency spectrum as compared tothe BS 806. The BSs 804 and 806 may communicate with each other.According to aspects, the BSs 804 and 806 may be co-located. The BS 806and UE 802 may communicate with each other using beams.

In accordance with one or more aspects, the BSs 804 and 806 may use thesame or different radio access technology (RAT), the same or differentfrequency band, and in some cases the BSs 804 and 806 may be the sameBS. For example, in some cases, the BSs 804 and 806 may be in twoneighboring cells using a same frequency and RAT such as a serving celland neighbor cell that is helping. In another case the BSs 804 and 806may use different carrier frequencies and/or RATs, for example one BScould use LTE and the other could use mmWave or NR, or one BS could usesub-6 GHz NR and the other could use mmWave NR. Further, in anotherexample, the BSs 804 and 806 may be co-located in one BS configured tooperate both sets of operations provided by the BSs 804 and 806 tocommunicate with a UE.

As described above, mmWave communication may be beam-formed, whereinwireless devices may communicate using directional beams. A UE 802receiving assistance, from BS 804, in accessing the BS 806 may simplifyaccess to the mmWave network. Additionally, assistance from the BS 804may help conserve mmWave resources. The conserved resources may increaseflexibility in the mmWave network. For example, the BS 806 may flexibly(e.g., dynamically) allocate directional synchronization and directionalRACH resources per demands of UEs.

Typically, UE's initial access to a network may involve performingsynchronization to acquire time, frequency, and system information ofthe serving BS. After synchronization, the UE may transmit a RACHpreamble to identify itself to BS. The UE and BS may complete theinitial access process by exchanging additional messages, including aRandom Access Response (message 2), message 3, and 4 during a RACHprocedure. According to aspects of the present disclosure, a UE 802 mayadvantageously not perform synchronization to the BS 806 prior totransmitting the RACH preamble.

Synchronization and random access (RACH) in an mmWave system may includethe transmission and reception of beam-formed signals. Thus,synchronization and random access may be referred to as directional SYNCand directional RACH. Synchronization and random access in lowerfrequency wireless communication system may be referred to as SYNC andRACH.

Two modes of directional SYNC and directional RACH may exist: assisteddirectional SYNC/RACH and typical, directional SYNC/RACH. Assisteddirectional SYNC/RACH may involve assistance from a BS 804 (e.g.operating in a lower frequency than BS 806) in performingsynchronization to/random access with the BS 806. The configuration ofassisted directional SYNC/RACH may be UE-specific. In one or more cases,the configuration may include a beam reference signal configuration.Further, an example of a beam reference signal includes, but is notlimited to, a channel state information reference signal (CSI-RS), whichmay be UE-specific. Typical directional SYNC/RACH may not includeassistance from the BS 804. The configuration for typical, directionalSYNC/RACH may be system/cell-specific and not UE-specific.

In some cases, two modes of RACH may exist: typical RACH (that may beused for initial access), and a dedicated RACH. The two modes of RACHmay have different sets of resources and/or configuration. In oneexample, they may be allocated orthogonal sets of resources in at leastone of a time (e.g. TDM), frequency (FDM), and code (CDM) spaces.Additionally/alternatively, the configuration of the dedicated RACH maybe different from the other RACH in terms of at least one of a preamblesequence related parameter (e.g. root sequence, cyclic shift, preambleindex), maximum number of transmissions, power control parameters (e.g.maximum number of power rampings, target received power, retransmissionpower ramping steps size), timer setting, association with other signals(e.g. synchronization and/or beam reference signals), and numerology.The dedicated RACH may be used for a different purpose than the other(typical) RACH. In one example, the dedicated RACH may be used forrecovery from a beam failure event. In some examples, the dedicated RACHmay be configured specifically for a UE. In another example, the twomodes of RACH may be used by two groups of wireless nodes (UEs, relays,BSs), based on their categories and capabilities. In one example, thefirst mode may be used by the UEs in the system and the second mode bythe relays.

In some cases, two modes of SYNC may exist: typical SYNC (that may beused for initial access) and a dedicated SYNC. The two modes of SYNC mayhave different sets of resources and/or configuration. In one example,they may be allocated orthogonal sets of resources in at least one of atime (e.g. TDM), frequency (FDM), and code (CDM) spaces.Additionally/alternatively, the configuration of the dedicated SYNC maybe different from the other SYNC in terms of at least one of a sequencerelated parameter (e.g. root sequence, cyclic shift of a synchronizationsignal (a primary synchronization signal, a secondary synchronizationsignal, a tertiary synchronization signal, a timing or frequencyrefinement signal), a beam reference signal, a demodulation referencesignal), a synchronization channel related parameters (e.g., content andconfiguration of a physical broadcast channel or a downlink control anddata channel that carry part of the system information), numerology,beam sweep periodicity (e.g. sync burst set periodicity), number ofsignals transmitted within a window (e.g. within a period), theinformation carried by the signals, association with other signals (e.g.synchronization and/or beam reference signals), and thequasi-collocation (QCL) assumption. The dedicated SYNC may be used for adifferent purpose than the other SYNC. In one example, the dedicatedSYNC may be used for one or more of a beam management, RRM, RLM, oraccess. In some examples, multiple dedicated SYNC may be configured(e.g. with different resources and/or configuration) for two or moredifferent procedures. For example, the first dedicated SYNC may beconfigured for RRM and the second dedicated SYNC may be configured forRLM. In some examples, the dedicated SYNC may be configured specificallyfor a UE. In another example, the two modes of SYNC may be used by twogroups of wireless nodes (UEs, relays, BSs), based on their categoriesand capabilities. In one example, the first mode may be used by the UEsin the system and the second mode by the relays.

As used herein, the term mmWave generally refers to spectrum bands invery high frequencies such as 28 GHz. Such frequencies may provide verylarge bandwidths capable of delivering multi-Gbps data rates, as well asthe opportunity for extremely dense spatial reuse to increase capacity.Traditionally, these higher frequencies were not robust enough forindoor/outdoor mobile broadband applications due to high propagationloss and susceptibility to blockage (e.g., from buildings, humans, andthe like).

Despite these challenges, at the higher frequencies in which mmWaveoperates, the small wavelengths enable the use of a large number ofantenna elements in a relatively small form factor. This characteristicof mmWave may be leveraged to form narrow directional beams that maysend and receive more energy, which may help overcome thepropagation/path loss challenges.

These narrow directional beams may also be utilized for spatial reuse.This is one of the key enablers for utilizing mmWave for mobilebroadband services. In addition, the non-line-of-site (NLOS) paths(e.g., reflections from nearby building) may have very large energies,providing alternative paths when line-of-site (LOS) paths are blocked.Aspects of the present disclosure may take advantage of such directionalbeams, for example, when a UE performs initial access, beam management,mobility management, RRM, and/or RLM with a mmWave base station (e.g.,and SeNB).

In some cases, the assisted access process may be provided between avariety of different wireless nodes/device combinations that are notlimited to that which is shown in FIG. 8. For example, the wirelessnodes may include a set of at least two wireless nodes that include anycombination of one or more of a gNBs, a relay(s), and a UE(s).Accordingly, the assisted access process may be provided over a numberof different communication implementations that depend from the specificwireless devices selected. For example, the communication may be any oneof backhaul (BH), integrated access and backhaul (IAB), and/or D2Dcommunication between two UEs. IAB may include the sharing of the sametechnology and the same resources shared between access links and/orbackhaul links. In some cases, a UE may operate and providecommunication abilities of a BS.

Example Directional Synchronization in Assisted Millimeter Wave Systems

In assisted mmWave access, different modes of operation may exist basedon the level of involvement of a primary BS. In one example, the primaryBS may provide a UE with a minimum amount of information fortransmitting a directional RACH preamble to a secondary BS.

With reference to FIG. 8, the BS 804 may provide the UE 802 with aminimum amount of information, such as the time/frequency resources fordirectional RACH transmission and directional RACH preambleconfiguration (e.g., choices of Zadoff-Chu root/cyclic shift, or thesubcarrier spacing), association between RACH resources and SYNC or beamreference resources or configuration, configuration of message2 of RACH(e.g., choice of subcarrier spacing for message2) for use incommunicating with the BS 806. In one example, at least part of theseresources and configurations are UE-specifically determined. Forexample, some time/frequency resources for RACH transmission may bededicated to the UE. According to certain aspects of the presentdisclosure, the UE 802 may, advantageously, not perform directional SYNCto the BS 806. The UE may bypass at least part of the synchronizationprocedure because of the assistance received from the BS 804.

In an assisted mmWave initial access procedure, there may be differentoperation modes, for example, based on the level of MeNB involvement. Inone method, the MeNB may at least provide directional SYNC configurationinformation to the UE to facilitate its directional synchronizationprocedure. The directional SYNC signal may include, for example, anycombination of signals, such as sync reference signals (e.g., such asPSS/SSS) or beam measurement reference signals (beam “MRS” or “BRS”).FIGS. 9 and 10 illustrate two examples of different operation modes formmWave assisted initial access. In one or more cases, the operationmodes may be used for beam management, mobility management, RRM, and/orRLM.

For example, FIG. 9 illustrates a first mode of operation for assistedinitial access that may be referred to as Operation Mode A.

As illustrated, in this mode of operation, an MeNB provides directionalSYNC/RACH configuration information to the UE. This information mayinclude, for example, at least time/frequency resources for the UE touse for directional initial access (e.g., a measurement window tomonitor and receive directional SYNC and/or beam reference signals). Anexample of a beam reference signal includes, but is not limited to, achannel state information reference signal (CSI-RS). In one or morecases a CSI-RS may be UE-specific. The configuration information mayalso include beam sweep periodicity of the SYNC signal (e.g., asynchronization burst set periodicity indicating how often transmit beamdirections are changed). The configuration information may also includean indication of a set of SYNC and/or beam reference signals that aretransmitted within the indicated time/frequency resources (e.g.,measurement window) and may be used by the UE for at least one of anaccess, beam management, mobility management, RRM, and/or RLMprocedures.

The configuration information may also include SYNC-RACH resource pairmapping (e.g. the association between RACH resources and synchronizationsignals, or the association between RACH resources and CSI-RS),quasi-collocated (QCL) information (information regarding QCL) of atleast a subset of sync signals, beam reference signals (CSI-RS), and/orRACH messages with each other or with other reference signals orchannels (e.g. QCL indication of two or more sync signals transmittedwithin a beam sweep period, QCL indication of sync signals on a firstfrequency band with sync signals on a second frequency band). Theassumption may indicate any level of QCL with respect to differentparameters, including spatial QCL, QCL with respect to average delay,delay spread, and/or Doppler shift or Doppler spread). The configurationmay also include SYNC-RACH reciprocity assumption, and/or a numerology(e.g., carrier spacing and/or cyclic prefix of at least one ofsynchronization signals and channels, CSI-RS, RACH message1, message2,message3, or message4). The configuration may also indicate that thetiming and synchronization of MeNB may be used to acquire at least partof the timing and synchronization of the SeNB.

The configuration information may also include one or more parametersassociated with the beam reference signals (e.g. CSI-RS) including,transmission periodicity, transmission bandwidth, time/frequencyresource locations, parameters for sequence generation, numerology,association with synchronization signals, QCL (e.g., spatial QCL)indication (e.g. via a state parameter or and index to a table).

The resource pair mapping may indicate, for example, what resources fora UE to use for sending a RACH transmission based on a received SYNCsignal. For example, the resources used for the RACH transmission mayindicate a best beam direction for the received SYNC signal (e.g., andthe SeNB may select a transmit direction accordingly for futurecommunications). The SYNC-RACH reciprocity assumption indication mayindicate whether a UE can assume SYNC-RACH reciprocity, for example,allowing the UE to determine the beam direction for the transmission ofthe RACH signal based on the beam direction of the received SYNC signal.

As illustrated in FIG. 9, during initial access according to operationmode A, the UE may acquire the directional SYNC signal. Acquiring thedirectional SYNC signal may involve one or more of acquiringtime/frequency synchronization (e.g. when MeNB and SeNB(s) are notsynchronized), acquiring the system information, or acquiring the beamstate information (finding the quality (or the best) of Tx/Rx beampair(s)).

After acquiring the SYNC signal, the UE then transmits a directionalRACH preamble based on the provided configuration information and theacquired SYNC signal. The UE may then receive a random access response(RAR) and complete the random access process with SeNB. In one or morecases, at least part of the operation mode shown in FIG. 9 may be usedfor beam management, mobility management, RRM, and/or RLM.

FIG. 10 illustrates a second mode of operation for assisted initialaccess that may be referred to as Operation Mode B.

In this mode, however, the MeNB may provide a different level ofsupport. For example, as illustrated, in this mode of operation, theMeNB may provide (only) directional SYNC configuration information tothe UE. This information may include, for example, time/frequencyresources for the UE to use for directional initial access (e.g., toreceive directional SYNC and/or beam reference signals (e.g. CSI-RS)),the beam sweep periodicity of the SYNC signal, a numerology of the SYNCsignal, QCL indication of synchronization or beam reference signals, andan indication of transmitted synchronization, or beam reference signalsthat can be used by the UE.

During initial access according to operation mode B, the UE may acquirethe directional SYNC signal using the configured resources/parameters.Rather than immediately send the directional RACH, however, the UE mayfirst send a measurement report (with a result of measuring) to MeNBincluding various information based on reception of the directional SYNCand/or beam reference signals (e.g., cell id, Tx/Rx beam id, and beamstate/quality).

The MeNB may coordinate with the SeNB(s) to determine the RACHconfiguration based on the submitted measurement report(s). The MeNB maythen send a directional RACH configuration message which may include,for example, one or more selected cell IDs, RACH resources, Tx/Rx beamid, RACH preamble information, and RACH Tx power information, RACHresource association with one or more of synchronization and beamreference signals, and/or numerology of RACH messages. In one or moreexamples, the directional RACH configuration may be provided from theMeNB to the UE via a handover message.

The UE and SeNB may then complete random access process based on theprovided configuration. In one or more cases, at least part of theoperation mode shown in FIG. 10 may be used for beam management,mobility management, RRM, and/or RLM.

Aspects of the present disclosure may help optimize such assistedinitial access, beam management, mobility management, RRM, and/or RLMprocedures. For example, according to certain aspects, the providedconfiguration/allocated resources of at least one of synchronizationsignals, beam reference signals (CSI-RS), RACH messages may bespecifically configured for a UE and may be different from the commonconfiguration resources.

Such UE-specific configuration information may be signaled to the UE byMeNB (e.g. using some dedicated signaling like an RRC message). FIGS.11-13 illustrate operations various entities involved in assisteddirectional initial access using such UE-specific configurationinformation.

For example, FIG. 11 illustrates example operations, which may beperformed by BS, according to aspects of the present disclosure. The BSmay include one or more modules of the BS 110 illustrated in FIG. 4. TheBS 110 may be a primary BS (MeNB) that communicates with one or moreUEs, for example, in a non-mmWave frequency spectrum.

At 1102, the primary BS communicates with at least one user equipments(UEs) in a first frequency band. At 1104, the primary BS determines atleast part of resources and configuration for the at least one UE forparticipating in at least one of an access or management procedure in asecond frequency band. At 1106, the primary BS provides informationabout the resources and configuration to the at least one UE forsignaling to be transmitted as part of the access or management process.In some cases, the information provided via at least one of: a layer-1signal, a media access control (MAC) control element (CE), a radioresource control (RRC) message, a broadcast channel, a control channel,or dedicated signaling.

In some cases, the primary BS may provide the information about theresources and configuration for the UE to participate in an access ormanagement procedure in a second frequency band with a second BS (e.g.,an SeNB). In other cases, UE assistance information may be provided by asingle base station. As described herein, in some cases, the informationprovided may be UE-specific, whether a single or multiple base stationsare involved. In the case a single BS is involved, that BS may provideUE-specific information to a UE to configure one or more (access ormanagement) procedures and participate in the procedures with that UEitself.

In one or more cases, the first frequency spectrum may be equal to thesecond frequency spectrum. In some cases, the operations may beimplemented for sub-6 GHz applications. Further, the procedures may beperformed with either the primary BS or the second BS.

FIG. 12 illustrates example operations, which may be performed by UE,according to aspects of the present disclosure.

At 1202, the UE communicates with a first base station (BS) in a firstfrequency band. At 1204, the UE receives, from the first BS, informationof at least part of resources and configurations for participating in atleast one of an access or management procedures in a second frequencyband. In some cases, the UE may receive the information of resources andconfigurations in response to signaling it sends. For example, a UE mayreceive the information after sending a request or a measurement report.The allocation of resources and configuration information from the firstBS may be for signaling (e.g., at least one of a directionalsynchronization signal, a beam reference signal, or a random accessmessage) to be transmitted by a second BS operating in a secondfrequency spectrum as part of at least one of an initial access, beammanagement, mobility management, radio resource management (RRM), orradio link monitoring (RLM) procedures, wherein the configurationinformation is specific to the UE or to a set of UEs including the UE.The directional synchronization signal comprises at least one of aprimary synchronization (PSS), a secondary synchronization signal (SSS),a tertiary synchronization signal (TSS), a timing or frequencyrefinement signal (TRS), a demodulation reference signal (DMRS) for asynchronization channel. In some cases, the UE may transmit, to thefirst BS, an indication including at least one of a measurement reportof one or multiple of synchronization signals and beam referencesignals, a set of one or more cell identifiers of at least one otherdetected base station, a request, or a capability of the UE. At 1206,the UE participates in the at least one of an access or managementprocess (e.g., assisted directional initial access, beam management,mobility management, RRM, or RLM) with the second BS in accordance withthe configuration information. In one or more cases, the first frequencyspectrum may be equal to the second frequency spectrum.

As noted above, in some cases, multiple base stations may be involved inthe UE-assisted approach described herein. For example, a BS of aneighboring cell may communicate with a BS of another cell serving a UEto provide assistance information. FIG. 13 illustrates exampleoperations, which may be performed, for example by a neighboring cellBS, according to aspects of the present disclosure. The BS may includeone or more modules of the BS 110 illustrated in FIG. 4. The BS 110 maybe a secondary BS (e.g., mmWave SeNB) that communicates with one or moreUEs, for example, in a mmWave frequency spectrum.

At 1302, the secondary BS communicating with at least a second BS (e.g.,MeNB). At 1304, the secondary BS determines at least part of resourcesand configuration for at least one UE for participating in at least oneof an access or management procedure. As described herein, the resourcesand configuration may be UE-specific. At 1306, the secondary BSprovides, to the second BS, information of the resources andconfiguration for the at least one UE for signaling to be transmitted aspart of the access or management process. At 1308, the secondary BSparticipates with the at least one UE in at the least one of an accessor management procedure.

As described herein, the resources and configuration information may beUE-specific. In some cases, the signaling may include at least one of adirectional synchronization signal, a channel carrying at least part ofsystem information, and the information may include at least one of atransmission periodicity, a beam sweeping periodicity, time andfrequency resources used for the transmission of the signaling, one ormore measurement windows to receive and measure a synchronizationsignal, a set of synchronization signals within a measurement window tomeasure, an indication of actually transmitted synchronization signals,quasi-collocated information of a synchronization signal with othersignals or channels, indication of synchronization signal repetitionwithin a beam sweeping period, subcarrier spacing, a sequence generationparameter for a synchronization signal.

In some cases, the secondary BS may configure one or multiple sets ofUE-specific resources for the transmission of the synchronizationsignals for the at least one UE for one or multiple of an access, beammanagement, RRM, and RLM procedures. In some cases, the secondary BS mayconfigure a UE-specific synchronization signal (TRS) for the at leastone UE for maintaining and refining at least one of a timing andfrequency synchronization.

In some cases, the signaling includes one or multiple beam referencesignals (e.g. CSI-RS), and the information includes at least one of atransmission periodicity, a transmission bandwidth, a beam sweepingperiodicity, time and frequency resources used for the transmission ofthe beam reference signals, one or more measurement windows to receiveand measure beam reference signals, a set of beam reference signalswithin a measurement window to measure, quasi-collocated information ofbeam references signal with other signals or channels, subcarrierspacing, a sequence generation parameter for beam reference signals,number of antenna ports. In such cases, the secondary BS may configureone or multiple sets of UE-specific beam reference signals for the atleast one UE for one or multiple of an access, beam management, RRM, andRLM procedures.

In cases where the access or management procedure includes a randomaccess procedure, the resource and configuration information may be fora UE to use for sending at least one of a first random access message ora second random access message to be transmitted to the at least one UE.For example, the information may include at least one of a set of timeand frequency resources for the transmission of the at least one of afirst random access message and a second random access message, anassociation between the resources of the at least one of a first randomaccess message and a second random access message with a set of at leastone or multiple of a synchronization signal and a beam reference signal,a QCL configuration with respect to other signals and channels, asubcarrier spacing, a preamble id, a cyclic shift, a power controlparameter, a max number of retransmissions of the first random accessmessage, or a subcarrier spacing of the second random access message.

In some cases, (UE-specific) resources and configuration may be based atleast on one of an indication from an upper layer, indication from thenetwork, indication from a second BS, measurements of the first BS, aset of pre-determined configurations, indication from the at least oneUE including at least one of a measurement report, a request, and UE'scapability indication. The secondary BS may receive a first message froma second BS and the secondary BS may transmit a second message to thesecond BS, as a response to the first message, providing information ofthe at least part or resources and configurations. The secondary BS maydetermine the at least part or resources and configurations based atleast on the first message. In some cases, the first message transmittedby the second BS may include at least one of a measurement report by theat least one UE, a request by the at least one UE, an indication of theat least one UE's capability.

Using UE-specific directional initial access configuration information,some resources may be allocated for directional SYNC transmission to oneor multiple UEs (e.g., within a set), within which the mmWave eNB maytransmit directional synchronization signal(s) based on some assisteddirectional SYNC configuration information.

In some cases, the configuration of the assisted directional SYNC signalmay be different from the typical cell-based directional SYNC signalconfiguration. For example, the SYNC signal configuration may bedetermined along with the allocated resources and be specific to theUE(s). Such UE-specific information may be signaled to the UE by theMeNB. In some cases, there may be a preconfigured set of candidateconfigurations. In such cases, the UE may be provided an indication ofone or multiple of the configurations in the pre-configured set.

As described herein, configuration information for a SYNC signal mayrefer to information related to the waveform of the SYNC and/or beamreference signals (e.g. CSI-RS). The configuration information mayfurther include, for example, RACH and/or SS. Such information mayinclude a PSS ID (e.g., a root of a Zadoff-Chu sequence used to generatePSS), SSS ID, and/or beam reference signal configuration.

Similarly, the allocated assisted directional SYNC resources may bedifferent (in time and/or frequency) from the typical cell-baseddirectional SYNC resources. In some cases, the SYNC resources may bespecific to the UE(s) and based on their demands (e.g. traffic and/orservice needs).

In some cases, UE-specific resources may be achieved by repurposing someresources used in common cell-based communications. For example, typicalcell-based PDSCH/PUSCH resources may be re-purposed and allocated forassisted directional initial access.

As described above, beam management procedures may utilize a number ofdifferent RS types. For example, a configuration may be signaled using aUE specific CSI-RS. Particularly, an RS defined for mobility purposes inat least a connected mode may be utilized. The RS may be a NR-SS, aCSI-RS, or a newly designed RS but is not limited thereto. The CSI-RSmay be specifically configured for a UE. In some cases, multiple UEs maybe configured with the same CSI-RS. The signal structure for CSI-RS maybe specifically optimized for a particular procedure. Further, CSI-RSmay also be used for CSI acquisition. Other RS could also be consideredfor beam management such as DMRS and synchronization signals.

The assisted access process described above may be referred to as anon-standalone (NSA) case. To support adaptation in such cases, anetwork (NW) indication of information may be provided to connectedand/or idle mode UEs, such as an SS burst set periodicity andinformation to derive measurement timing/duration (e.g., time window forNR-SS detection).

In some cases, properties or a configuration of synchronization signal(SS) or CSI-RS used for mobility may be signaled to a UE using dedicatedsignaling. In some cases, the NW may provide a parameter that is validfor CSI-RS resources associated with detected cells on a carrierfrequency (e.g. based on UE measurement reporting). In some cases,CSI-RS configuration may be provided via UE specific signaling (e.g., ina handover command). In some cases, a serving cell may provideinformation that assists a UE in deriving the reference time of a targetcell in a synchronous system.

In some cases, for contention-free access, dedicated RACH resources maybe provided in the time domain different from resources used forcontention-based access. For example, a UE may be configured to transmitmultiple Msg.1 over dedicated multiple RACH transmission occasions inthe time domain before the end of a monitored RAR window. In such cases,the multiple Msg.1 can be transmitted with the same or different UE TXbeams.

As described herein, in some cases, multiple (two or more) sets ofresources and configurations may be used for procedures such as RACH orSS transmission. The multiple sets may allow for dedicated RACH w/different time resources, dedicated RACH for beam failure recovery,UE-specific PRACH sequences, specific RACH configurations, TDM withother PRACH transmission, different QCL configurations (e.g., forSS/CSI-RS), and/or FDM or CDM with other PRACH transmissions. Multiplesets for SS transmissions may allow for a first set of SS signals for afirst set of nodes (e.g. UEs) and a second set for a second set of nodes(e.g. relays). Different sets of resources may be used for differentpurposes (e.g. RLM, RRM, beam management, initial access), and they mayadditionally have UE-specific resource configurations.

FIGS. 14-16 illustrate example operations that may be performed by aprimary BS, a secondary BS, and a wireless node (WN) such as a UE or arelay, respectively, utilizing multiple sets of resources.

Operations 1400 of FIG. 14 begin, at 1402, by determining a first set ofat least part of resources and configuration for the at least onewireless node (WN) for participating in at least one of an access ormanagement procedure. At 1404, the primary BS determines a second set ofat least part of resources and configuration for at least one of anaccess or management procedure. At 1406, the primary BS provides(directly or indirectly) information of at least one of the first setand the second set to the at least one WN for signaling to betransmitted as part of the access or management process. At 1408, theprimary BS participates in at least one of access or managementprocedure using at least one of the first set and the second set.

Operations 1500 of FIG. 15 begin, at 1502, by communicating with atleast one wireless node (WN). At 1504, the secondary BS determines afirst set of at least part of resources and configuration for the atleast one wireless node (WN) for participating in at least one of anaccess or management procedure with a second BS. At 1506, the secondaryBS transmits at least one or more signals to the at least on WN toprovide information of the first set for signaling to be transmitted aspart of the access or management process.

Operations 1600 of FIG. 16 begin, at 1602, by receiving information of afirst set of at least part of resources and configuration forparticipating in at least one of an access or management procedure witha first base station (BS). At 1604, the UE receives information of asecond set of at least part of resources and configuration for at leastone of an access or management procedure with the first BS. At 1606, theUE participates in at least one of access or management procedure usingat least one of the first set and the second set with the first BS. Insome cases, it is indicated to the UE when to use the first set and thesecond set, for example based on the procedure the UE is performing, thestate of the UE, the operation mode of the UE, or the capabilities ofthe UE. In some cases, it is left to the UE to decide when to use thefirst set and the second set for participating in an access ormanagement procedure with the first BS.

In some cases, the first set may include resources that were at least inpart allocated for at least one of physical downlink shared channel(PDSCH) or physical uplink shared channel (PUSCH) resources. In somecases, the set may include resources that at least in part overlap withthe resources of the second set. In other cases, the first and secondset of resources may be non-overlapping. The first set may be configuredspecific to the at least one WN (e.g., a UE) or a plurality of WNsincluding the at least one WN, while the second set may be configuredcommonly in a cell specific manner.

In some cases, the first set is configured for a first category of WNs,and the second set for the second category of WNs, wherein the firstcategory and the second category may differ in at least one of:capabilities, demands, states, modes of operation, procedures they areperforming. The first category may be a set of UEs, and the secondcategory may be a set of relays.

In some cases, the primary BS is communicating with at the least one WN,and providing the information is based on transmitting one or moresignals to the at least one WN. In some cases, the primary BS maycommunicate with a second BS (e.g., a secondary BS), and provide theinformation to the second BS. In such cases, the primary BS may receiveat least one or more first signals from the second BS and transmit atleast one or more second signals to the second BS, as a response to thereceived one or more first signals, to provide the information. Theprimary BS may also determine the first set of resources andconfigurations at least in part based on the one or more first signalsreceived from the second BS.

In some cases, participating in the at least one of access or managementprocedure comprises receiving or monitoring at least one of a firstrandom access message and transmitting at least a second random accessmessage in response to the first random access message. Accordingly, thefirst set and the second set are different in terms of at least one of:a transmission periodicity, a beam sweeping periodicity, one or moremeasurement windows to receive and measure a synchronization signal or abeam reference signal, a set of synchronization signals or beamreference signals within a measurement window to measure, an indicationof actually transmitted synchronization signals a set of time andfrequency resources for the transmission of the at least one of a firstrandom access message and a second random access message, an associationbetween the resources of the at least one of a first random accessmessage and a second random access message with a set of at least one ormultiple of a synchronization signal and a beam reference signal, a QCLconfiguration with respect to other signals and channels, a subcarrierspacing, a preamble id, a cyclic shift, a power control parameter, a maxnumber of retransmissions of the first random access message, asubcarrier spacing of the second random access message, or theinformation comprises at least one of the above aspects. The first setof resources and configurations for the random access procedure may beconfigured for a beam failure recovery for the at least one WN, and thesecond set of resources and configuration is configured for a commonrandom access procedure. The resources of the first set and the secondset may be multiplexed in at least one of a frequency domain (FDM), timedomain (TDM), code domain (CDM).

In some cases, the first set of resources and configurations may beconfigured for a dedicated random access procedure by the at least oneWN, and the second set of resources and configuration may be configuredfor a common random access procedure. In such cases, the first set mayoccupy a different set of time resources than the second set.

The primary BS may determine at least part of resources andconfiguration (of the first and/or second set) based at least on one of:an indication from an upper layer, indication from the network,indication from a second BS, measurements of the first BS, a set ofpre-determined configurations, indication from the at least one WNincluding at least one of a measurement report, a request, and WN'scapability indication.

In some cases, the secondary BS may determine a second set of at leastpart of resources and configuration for at least one of an access ormanagement procedure of the second BS and transmit at least one or moresignals to the at least one WN to provide information of the second setfor signaling to be transmitted as part of the access or managementprocess.

In some cases, the UE may also communicate with the second BS, andreceive at least one or more signals from the second BS indicating theinformation. The UE may also transmit at least one or more first signalsto the second BS, including at least one of a request, a report ofmeasurement of one or more synchronization signals and beam referencesignals, capabilities of the WN, and receive the at least one or moresignals from the second BS, as a response to the one or more firstsignals.

The methods described herein comprise one or more steps or actions forachieving the described method. The method steps and/or actions may beinterchanged with one another without departing from the scope of theclaims. In other words, unless a specific order of steps or actions isspecified, the order and/or use of specific steps and/or actions may bemodified without departing from the scope of the claims.

As used herein, a phrase referring to “at least one of” a list of itemsrefers to any combination of those items, including single members. Asan example, “at least one of: a, b, or c” is intended to cover a, b, c,a-b, a-c, b-c, and a-b-c, as well as any combination with multiples ofthe same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b,b-b-b, b-b-c, c-c, and c-c-c or any other ordering of a, b, and c).

As used herein, the term “determining” encompasses a wide variety ofactions. For example, “determining” may include calculating, computing,processing, deriving, investigating, looking up (e.g., looking up in atable, a database or another data structure), ascertaining and the like.Also, “determining” may include receiving (e.g., receiving information),accessing (e.g., accessing data in a memory) and the like. Also,“determining” may include resolving, selecting, choosing, establishingand the like.

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the claims are not intended to be limited to theaspects shown herein, but is to be accorded the full scope consistentwith the language of the claims, wherein reference to an element in thesingular is not intended to mean “one and only one” unless specificallyso stated, but rather “one or more.” Unless specifically statedotherwise, the term “some” refers to one or more. All structural andfunctional equivalents to the elements of the various aspects describedthroughout this disclosure that are known or later come to be known tothose of ordinary skill in the art are expressly incorporated herein byreference and are intended to be encompassed by the claims. Moreover,nothing described herein is intended to be dedicated to the publicregardless of whether such disclosure is explicitly recited in theclaims. No claim element is to be construed under the provisions of 35U.S.C. § 112, sixth paragraph, unless the element is expressly recitedusing the phrase “means for” or, in the case of a method claim, theelement is recited using the phrase “step for.”

The various operations of methods described above may be performed byany suitable means capable of performing the corresponding functions.The means may include various hardware and/or software component(s)and/or module(s), including, but not limited to a circuit, anapplication specific integrated circuit (ASIC), or processor. Generally,where there are operations illustrated in figures, those operations mayhave corresponding counterpart means-plus-function components withsimilar numbering.

The various illustrative logical blocks, modules and circuits describedin connection with the present disclosure may be implemented orperformed with a general purpose processor, a digital signal processor(DSP), an application specific integrated circuit (ASIC), a fieldprogrammable gate array (FPGA) or other programmable logic device (PLD),discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general-purpose processor may be a microprocessor, but in thealternative, the processor may be any commercially available processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

If implemented in hardware, an example hardware configuration maycomprise a processing system in a wireless node. The processing systemmay be implemented with a bus architecture. The bus may include anynumber of interconnecting buses and bridges depending on the specificapplication of the processing system and the overall design constraints.The bus may link together various circuits including a processor,machine-readable media, and a bus interface. The bus interface may beused to connect a network adapter, among other things, to the processingsystem via the bus. The network adapter may be used to implement thesignal processing functions of the PHY layer. In the case of a userterminal 120 (see FIG. 1); a user interface (e.g., keypad, display,mouse, joystick, etc.) may also be connected to the bus. The bus mayalso link various other circuits such as timing sources, peripherals,voltage regulators, power management circuits, and the like, which arewell known in the art, and therefore, will not be described any further.The processor may be implemented with one or more general-purpose and/orspecial-purpose processors. Examples include microprocessors,microcontrollers, DSP processors, and other circuitry that can executesoftware. Those skilled in the art will recognize how best to implementthe described functionality for the processing system depending on theparticular application and the overall design constraints imposed on theoverall system.

If implemented in software, the functions may be stored or transmittedover as one or more instructions or code on a computer readable medium.Software shall be construed broadly to mean instructions, data, or anycombination thereof, whether referred to as software, firmware,middleware, microcode, hardware description language, or otherwise.Computer-readable media include both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. The processor may beresponsible for managing the bus and general processing, including theexecution of software modules stored on the machine-readable storagemedia. A computer-readable storage medium may be coupled to a processorsuch that the processor can read information from, and write informationto, the storage medium. In the alternative, the storage medium may beintegral to the processor. By way of example, the machine-readable mediamay include a transmission line, a carrier wave modulated by data,and/or a computer readable storage medium with instructions storedthereon separate from the wireless node, all of which may be accessed bythe processor through the bus interface. Alternatively, or in addition,the machine-readable media, or any portion thereof, may be integratedinto the processor, such as the case may be with cache and/or generalregister files. Examples of machine-readable storage media may include,by way of example, RAM (Random Access Memory), flash memory, ROM (ReadOnly Memory), PROM (Programmable Read-Only Memory), EPROM (ErasableProgrammable Read-Only Memory), EEPROM (Electrically ErasableProgrammable Read-Only Memory), registers, magnetic disks, opticaldisks, hard drives, or any other suitable storage medium, or anycombination thereof. The machine-readable media may be embodied in acomputer-program product.

A software module may comprise a single instruction, or manyinstructions, and may be distributed over several different codesegments, among different programs, and across multiple storage media.The computer-readable media may comprise a number of software modules.The software modules include instructions that, when executed by anapparatus such as a processor, cause the processing system to performvarious functions. The software modules may include a transmissionmodule and a receiving module. Each software module may reside in asingle storage device or be distributed across multiple storage devices.By way of example, a software module may be loaded into RAM from a harddrive when a triggering event occurs. During execution of the softwaremodule, the processor may load some of the instructions into cache toincrease access speed. One or more cache lines may then be loaded into ageneral register file for execution by the processor. When referring tothe functionality of a software module below, it will be understood thatsuch functionality is implemented by the processor when executinginstructions from that software module.

Also, any connection is properly termed a computer-readable medium. Forexample, if the software is transmitted from a website, server, or otherremote source using a coaxial cable, fiber optic cable, twisted pair,digital subscriber line (DSL), or wireless technologies such as infrared(IR), radio, and microwave, then the coaxial cable, fiber optic cable,twisted pair, DSL, or wireless technologies such as infrared, radio, andmicrowave are included in the definition of medium. Disk and disc, asused herein, include compact disc (CD), laser disc, optical disc,digital versatile disc (DVD), floppy disk, and Blu-ray® disc where disksusually reproduce data magnetically, while discs reproduce dataoptically with lasers. Thus, in some aspects computer-readable media maycomprise non-transitory computer-readable media (e.g., tangible media).In addition, for other aspects computer-readable media may comprisetransitory computer-readable media (e.g., a signal). Combinations of theabove should also be included within the scope of computer-readablemedia.

Thus, certain aspects may comprise a computer program product forperforming the operations presented herein. For example, such a computerprogram product may comprise a computer-readable medium havinginstructions stored (and/or encoded) thereon, the instructions beingexecutable by one or more processors to perform the operations describedherein.

Further, it should be appreciated that modules and/or other appropriatemeans for performing the methods and techniques described herein can bedownloaded and/or otherwise obtained by a user terminal and/or basestation as applicable. For example, such a device can be coupled to aserver to facilitate the transfer of means for performing the methodsdescribed herein. Alternatively, various methods described herein can beprovided via storage means (e.g., RAM, ROM, a physical storage mediumsuch as a compact disc (CD) or floppy disk, etc.), such that a userterminal and/or base station can obtain the various methods uponcoupling or providing the storage means to the device. Moreover, anyother suitable technique for providing the methods and techniquesdescribed herein to a device can be utilized.

It is to be understood that the claims are not limited to the preciseconfiguration and components illustrated above. Various modifications,changes and variations may be made in the arrangement, operation anddetails of the methods and apparatus described above without departingfrom the scope of the claims.

What is claimed is:
 1. A method for wireless communication by a firstbase station (BS), comprising: communicating with a user equipment (UE)in a first frequency band; determining measurement information of adirectional synchronization signal in a second frequency band of asecond BS; and providing the measurement information to the UE, themeasurement information configured to assist the UE during performanceof a directional access procedure comprising a plurality ofcommunications in the second frequency band between the UE and thesecond BS by assisting in bypassing at least one of the plurality ofcommunications between the UE and the second BS, wherein the at leastthe one of the plurality of communications comprises a directionalsynchronization communication with the second BS, wherein themeasurement information comprises: time and frequency resources for theUE to use to initiate the directional access procedure; andquasi-collocation (QCL) information indicating a QCL relationshipbetween the directional synchronization signal in the second frequencyband and one or more other synchronization signals in another frequencyband.
 2. The method of claim 1, wherein the second frequency bandoperates within a mmWave spectrum, and wherein the first frequency bandoperates in a lower frequency spectrum relative to the mmWave spectrum.3. A first base station (BS) configured for wireless communication,comprising: a memory; and a processor communicatively coupled to thememory, the processor configured to: communicate with a user equipment(UE) in a first frequency band; determine measurement information of adirectional synchronization signal in a second frequency band of asecond BS; and provide the measurement information to the UE, themeasurement information configured to assist the UE during performanceof a directional access procedure comprising a plurality ofcommunications in the second frequency band between the UE and thesecond BS by assisting in bypassing at least one of the plurality ofcommunications between the UE and the second BS, wherein the at leastthe one of the plurality of communications comprises a directionalsynchronization communication with the second BS, wherein themeasurement information comprises: time and frequency resources for theUE to use to initiate the directional access procedure; andquasi-collocation (QCL) information indicating a QCL relationshipbetween the directional synchronization signal in the second frequencyband and one or more other synchronization signals in another frequencyband.
 4. The first BS of claim 3, wherein the second frequency bandoperates within a mmWave spectrum, and wherein the first frequency bandoperates in a lower frequency spectrum relative to the mmWave spectrum.5. A method of wireless communication by a user equipment (UE),comprising: communicating with a first base station (BS) in a firstfrequency band; receiving, from the first BS, measurement informationconfigured to assist the UE during performance of a directional accessprocedure between the UE and a second BS in a second frequency band, thedirectional access procedure comprising a plurality of communicationsbetween the UE and the second BS, wherein the measurement informationcomprises: time and frequency resources for the UE to use to initiatethe directional access procedure; an indication of a directionalsynchronization signal that is transmitted by the second BS within thetime and frequency resources; and quasi-collocation (QCL) informationindicating a QCL relationship between the directional synchronizationsignal in the second frequency band and one or more othersynchronization signals in another frequency band; and utilizing themeasurement information: initiating the directional access procedurebetween the UE and the second BS in the second frequency band; andbypassing at least one of the plurality of communications between the UEand the second BS, wherein the at least the one of the plurality ofcommunications comprises a directional synchronization communicationwith the second BS.
 6. The method of claim 5, wherein the secondfrequency band operates within a mmWave spectrum, and wherein the firstfrequency band operates in a lower frequency spectrum relative to themmWave spectrum.
 7. A user equipment (UE) configured for wirelesscommunication, comprising: a memory; and a processor communicativelycoupled to the memory, the processor configured to: communicate with afirst base station (BS) in a first frequency band; receive, from thefirst BS, measurement information configured to assist the UE duringperformance of a directional access procedure between the UE and asecond BS in a second frequency band, the directional access procedurecomprising a plurality of communications between the UE and the secondBS, wherein the measurement information comprises: time and frequencyresources for the UE to use to initiate the directional accessprocedure; an indication of a directional synchronization signal that istransmitted by the second BS within the time and frequency resources;and quasi-collocation (QCL) information indicating a QCL relationshipbetween the directional synchronization signal in the second frequencyband and one or more other synchronization signals in another frequencyband; and utilizing the measurement information: initiate thedirectional access procedure between the UE and the second BS in thesecond frequency band; and bypass at least one of the plurality ofcommunications between the UE and the second BS, wherein the at leastthe one of the plurality of communications comprises a directionalsynchronization communication with the second BS.
 8. The UE of claim 7,wherein the second frequency band operates within a mmWave spectrum, andwherein the first frequency band operates in a lower frequency spectrumrelative to the mmWave spectrum.